The concern follows a recent survey by South Africa's Medical Research Council which showed that one in four men have admitted committing rape, with 46 percent admitting they have raped more than once.

Researchers interviewed 1,738 men of all race groups.

A campaign group said it is now working with traditional leaders to change the practice.

Mbulelo Dyasi of Masimanyane, a women's support centre in east London, told the Independent Online website: "This is not part of our tradition; this is crime.”

Dyasi said groups fear that ritual sexual violence is being encouraged by widespread myths in areas such as the Eastern Cape, Western Cape and Mpumalanga.

She said young men fresh from initiation schools are being taught that they should first have sex with women who are not their partners to clean the penis and test if it working.

Nono Eland of the Treatment Action Campaign told the website that young initiates are encouraged to first have sex - without a condom – with people seen to be of "lesser value" in the community, such as women who had previously had many sexual partners.

Eland added that some also join gangs where members encourage new recruits to commit rape as a sign of good luck after circumcision. This increased the risk of exposure to HIV, Eland said.

The Eastern Cape House of Traditional Leaders is now revising the guidelines for initiation schools, to be released by December.